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Voltage controlled oscillator and non-inverting schmitt trig

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Apr 24, 2009
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non inverting schmitt trigger

Hello! Can anybody please explain to me how the schmitt trigger in both circuits and the voltage controlled oscillator in the link work? I couldn't figure it out especially the non inverting schmitt trigger part.

Here is the link from notes of IIT Madras: **broken link removed**

Added after 42 minutes:


Re: Voltage controlled oscillator and non-inverting schmitt

**broken link removed**

The upper circuit (opa1) is an integrator. That means that output voltage changes over time. How fast it change depends of voltage input, and it is inverted.

The lower circuit (opa2) is an schmitt-trigger. This one is non-inverting. Output voltage from this one can be only maximum or minimum (those values depends on opamp model and supply voltages).

We have to start somewhere. Say that output from opa1 is low. Then output from opa2 will also be low. But this means the voltage output from opa1 (integrator) will rise.

When output from opa1 have reached a certain level (upper hysterese on schmitrigger), voltage output from opa2 will go high.
This makes output voltage from opa1 (integrator) to fall. And it will fall util it reach the lower hysterese level for opa2.

And then it repeats, going up and down. Voltage out from opa1 will fall and rise between the two hysterese levels on the lower circuits, and here you'll get the ^^^ (english form for this waveform?) output while the output from opa2 will be squarewave because it shift between high and low voltage.

I haven't get hang on the VCO yet, so i pass it over to somebody else :|

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